Our invention relates to a compound diode assembly generally known as a twin-- or dual-diode assembly having two or more diode elements formed on a common semiconductor substrate to provide a common cathode. More particularly, our invention deals with means in such diode assemblies for the reduction of leakage current from one diode element to the other.
The common-cathode twinassembly has been known (FIG. 1) and used for rectification or for rectification and ripple filtration in switching regulators. The twin diode assembly has two pn-junction diodes, or Schottky-barrier diodes having guard rings, formed on a common semiconductor substrate having a cathode common to both diodes. As heretofore constructed, the twin diode assembly has been susceptible to the flow of leakage current from either diode to the other, with the consequent power loss. The leakage current is such that when the first diode of the twin diode assembly is forward-biased, for example, and the second reverse-biased, then a substantial proportion of the anode current of the first diode tends to flow to the anode of the nonconducting second diode instead of to the common cathode. We will later discuss why such leakage current flows in the twin diode assembly of conventional make.
We cite Japanese Unexamined Utility Model Publication No. 62-204357, laid open to public inspection on Dec. 26, 1987, as a known attempt at the reduction of the leakage current. This attempt, however, has met with only a limited success. There have been consistent demands in the electronics industry for twin diode assemblies that are far more free from leakage current and, therefore, from power loss.